Because the wall reflects sound waves to your ears bouncing off of the walls, even if it's in another room.
In order from shortest to longest frequency, the electromagnetic waves can be ranked :
1. X-rays
2. Ultraviolet
3. Infrared
4. Microwave
X-rays has the shortest frequency which ranges between 30 petahertz to 30 exahertz. X-rays have the smallest wavelengths at 0.01-10 nanometers. Its energy ranges between 100eV to 100keV.
So that there isn't too much force restricting the structure of the circus and cause disaster
//////Correct answer is C.///////